Artificial Lighting For African Violet Plants: Part II LED Lighting

Artificial Lighting For African Violet Plants: Part II LED Lighting

What are LED Lights:

  • Light Emitting Diodes are known as LED.
  • They are small in size, as a result a large number of LEDs can fit into an electrical circuit.
  • LEDs are semi-conductor diodes which can emit light. The LED bulb is enclosed in a transparent plastic hemispherical shaped shell/dome (see diagram below).
  • The LED bulb consists of two semiconducting materials between its electrodes. These are the p-type semiconductor and the n-type semiconductor material.
  • The p-type semiconductor is connected to the positive electrode (the anode terminal) and the n-type semiconductor material is connected to the negative electrode (the cathode terminal). By connecting these two materials the “p-n junction” is formed (see diagram below).
  • When the electric current is turned on the negatively charged electrons move across over to the positively charged region.
  • Due to the movement of these electrons energy is released in the form of light.
  • Light emitted from an LED can be of any wavelength and color, including ultraviolet or infrared.
  • These colors include, red, bright blue, white, orange, green, violet, purple and ultraviolet.
  • The type of color emitted from the LEDs depends upon the type of semiconductor material used in the LED.

How do LED lights generate light?

  • They are small in size and contain no filaments like regular light bulbs.
  • Instead of a filament, an LED creates light by electroluminescence in a semiconductor material.
  • Electroluminescence is when a semiconductor material emits light after electricity (electrical current) passes through or moves through the semiconductor material (see above p-n junction image).
  • As the electrons present within the electrical current, pass along the semiconductor material, it creates electromagnetic radiation, which can take the form of visible light.

LED Lights Compared To Fluorescent Lights:

  • LEDs use less energy than fluorescent lights.
  • They cost more than fluorescent lights, however last much longer.
  • LEDs do not generate heat as compared to fluorescent lights, so they can be kept closer to your violets and no risk of burning them.
  • LED lights direct light directly above the plant (in one direction), whereas fluorescent light emits diffused light (light in all directions).
  • Fluorescent lights are available in cool white, warm white or daylight bulbs.
  • LED bulbs are also available in cool white, warm white or daylight bulbs.
  • The technical difference between these bulbs is the color temperature. The unit measurement for color temperature is known as kelvin (K).
  • Learn more about color temperature range, here, “Part I Fluorescent Lighting”.
  • LED lights can be customized based upon wavelength and color temperature of the lights.

African Violet Plants Underneath LED Lights:

Replacement LED Tube Light Bulbs:

  • LED tube light bulbs are similar in shape to the fluorescent tube light bulbs.
  • Some of these LED bulbs have an on/off switch and some are dimmable too.
  • Since many growers already have invested in light fixtures for the T8 and T12 fluorescent bulbs, replacing the bulbs with LED makes sense, cost wise.
  • There are many types of LED replacement tube bulbs for T8 or T12 fluorescent bulbs.
  • First you need to find out what type of fluorescent bulbs you have, either a T8 or a T12 bulb.
  • There are markings at the end of the bulbs which should mention the type of bulb.
  • Second determine what pin size is your bulb, is it a T5 (5mm between pins) or T8 / T12 (13mm between pins). This is another way of confirming what kind of bulb you have.
  • Third, make sure you select the correct tube length. Finally, you have to confirm what type of ballast your fluorescent bulb runs on.
  • The T8 bulbs run on electrical ballasts and the T12 bulbs run on magnetic ballasts.
  • When choosing replacement LED tubes, you can either choose ballast compatible or a ballet bypass-direct line voltage LEDs tube (explained below).
  • Also when choosing LED tubes, you have to consider whether they are single ended or double ended tubes (explained below).

LED replacement T8 tube light bulbs:

  • These LED tube light bulbs are electronic ballast compatible tubes.
  • They are also known as “Type-A” or “Plug-n-Play” or “Direct-Fit” bulbs.
  • These work with electrical ballast similar to those found in T8 fluorescent tube fixtures.
  • These LED tubes will not work with magnetic ballast found in T12 fluorescent tube fixtures.
  • They need a T8 electrical ballast to work. This way you can still use your existing ballast and fixtures.
  • For this to work, just remove your T8 fluorescent tube and replace with a T8 LED tube.
  • Disadvantages of these bulbs are high cost.
  • Also the ballast fixture will stop working before the lifespan of your LED tube ends. As result you end up with the added cost of another fixture.

Direct-wire/Ballast bypass LED tubes: 

  • They are also known as “Type-B” or “Line Voltage” or “Direct-Wire” LED tubes.
  • There are two versions of Type –B tubes, single end powered (SEP) tubes and double end powered (DEP) tubes. These are discussed in more detail below.
  • These types of tubes are known as ballast bypass since the ballast needs to be bypassed or removed.
  • These LED tubes have an internal driver and are wired to the main line voltage. 
  • They run directly off the line voltage, “bypassing” the ballast. This means that the ballast is removed from the existing fixture and the power is wired directly to the sockets.
  • This is best done by a certified electrician unless you are comfortable working with simple wiring and can follow UL (underwriter laboratories) safety guidelines.
  • Ballast bypass requires simple rewiring of your current fixtures.
  • Specific instructions on how to change your current ballast fixtures to accommodate the new LED bulbs vary based upon the manufacturer of the replacement bulbs and the manufacturer of your fixtures.
  • There are numerous videos which can walk through these steps depending upon the type of current fixture you own and the type of replacement LED bulb you select.
  • This type of installation requires you to remove ballast cover, disconnect the wires, remove the ballasts on your fixtures and reconnect the wires.
  • These bulbs are cheaper than the ballast compatible bulbs.
  • They are more energy efficient then the ballast compatible bulbs.
  • They do however require the ballast to be bypassed or removed, as these LED bulbs do not require ballasts, but run on your home wiring.
  • By removing the ballast, you also remove the risk of ballast failure/replacement or ballast/tube incompatibility. 

Hybrid (electric ballast compatible + ballast bypass):

  • These tube light bulbs are also known as Type A+B or combo drive LED.
  • These LED tube light bulbs work with both ballast and non-ballast (line-voltage) installation.
  • If you are using an electrical ballast (for T8), then if the ballast stops working, you can rewire the LED tubes to connect directly to the line voltage.
  • This will require the help of a certified electrician, adding to costs.

Universal LED replacement tube light bulbs:

  • They can be used with T12 magnetic ballast or T8 electrical ballast.
  • Universal LED tube light bulbs are known as ballast compatible which means that you don’t have to change/remove your ballast.
  • The universal fit LED replacement bulbs can directly fit into your current fixtures.
  • No re-wiring is required, the LED bulbs fit into the same ballast as the fluorescent bulbs. Just remove the old fluorescent tubes and install the new LED tubes.
  • These work for both the T8 electrical ballast and the T12 magnetic ballast.
  • They come in three types, cool, daylight and warm.
  • However, there have been concerns with flickering, non-efficient output and low-energy efficiency with these direct universal replacement bulbs.
  • The cost of these universal bulbs is also high.
  • Also, if your ballast stops working, then of course you are left with replacing the whole fixture, which can lead to additional costs.

SEP or DEP powered tubes: SEP or DEP are two different types of Direct-wire/Ballast bypass/Type-B LED tubes (mentioned above).

(a) Single end powered tube (SEP):

  • Single end powered tube (SEP) take power from only one end of the tube.
  • The powered end of the tube is a non-shunted socket (a socket with separate points of contacts for the wires).
  • The other end of the tube is a dummy (no power).
  • SEP LED tubes will only operate on a non-shunted socket.
  • You will have to verify that your fixture has a non-shunted socket installed before using SEP LED tubes.
  • In SEP LED tubes, the power is wired through only one end of the tube.
  • SEP LED tubes eliminate the need for an external driver or ballast.
  • They have live and neutral pins on one single side of the socket.
  • This is known as the input end of the tube.
  • These tubes are direct wire and do not require a ballast to work.
  • If you are using these SEP LED tubes in an existing fluorescent fixture, then you will have to remove the ballast.
  • Both live and neutral pins are carriers of electric current.
  • When replacing SEP fluorescent tubes, you will need to replace the tubes, the fixture, and /or rewire the old fixture.
  • One of the risks of replacing the SEP tubes is tube failure or sparking.

(b) Double end powered tube (DEP):

  • Double end powered tube (DEP) means power is wired through the tube on both ends (the contacts are internally connected).
  • DEPs will only operate on shunted sockets (a connected socket).
  • Shunted sockets have two live pins on either side of the tube.
  • So they contain live pins on one end of the tube and neutral pins on the other end of the tube.
  • They both receive line voltage. DEP are similar to how fluorescent tubes runs.
  • Power is sent to both ends of the tubes with one end running line voltage and the other is neutral.
  • Fluorescent tubes are traditionally DEP tubes, so they can be easily replaced with a DEP LED tube.
  • The cost of DEP LED tubes are higher.

LED Shoplights:

  • If you don’t want to re-use your original fluorescent fixtures, another option is to purchase LED shoplights.
  • You can purchase these in 3ft or 4ft length.
  • They are available in similar color temperatures as fluorescent bulbs. So if your fluorescent bulbs were in the color temperature range of 3000K-4000K or 5000K-7000K, you can get similar LED bulbs too.
  • The warm white bulbs have a color temperature range from 2500K-3000K.
  • The cool white bulbs have a color temperature range from 3100K to 4500K.
  • The daylight bulbs have a color temperature range from 4600K to 6500K. Learn more about color temperature range, here, “Part I Fluorescent Lighting”.
  • I personally use cool white bulbs in my plant room, both fluorescent and LED.
  • Another factor to take into consideration is the lumens of the bulb.
  • This is very important when purchasing LED shoplights, as LED bulbs can be very bright. The higher the lumens, the brighter the bulbs.
  • For African Violets I would recommend to stay in the range of 2000-4000 lumens.
  • Anything higher would be too bright and may lead to tight crowns. If you do decide to go higher lumens, these would be similar to daylight bulbs, you would have to adjust the distance of plants from the lights and the duration the lights are on.
  • Higher lumen shoplights, may be suitable for seed germination or starter transplant plants.
  • Another reason to choose lower lumen bulbs, fluorescent tube bulbs have a cylindrical design, which means the light is diffused in all directions.
  • So if you have a fluorescent tube of 3000 lumen, your African Violet plant is only being exposed to 1000 lumen (a third of light) of light directly. However, when you change to LED bulbs, they shine light directly above the plant, so now your African Violet is receiving the total 3000 lumens of light.
  • That’s a big change for the plant and all that light, may lead to tighter crowns, crunchy, yellow or curled leaves.
  • I have started to use 3000 lumens cool white LED shoplights in my plant room. This is my 3ft one and my 4ft one.
  • I only have one LED shoplight per shelf, it does work well.
  • However, I have noticed I have to rotate the plants regularly for the leaves to get even light, otherwise the leaves are constantly reaching for the light and the plant grows lopsided.
  • I could adjust the height of the lights from the plants, maybe the duration too, but have not done so yet. I could also add one more daylight shoplight (4600K- 6500k), to the shelf along with the cool white, to provide a balanced light set up.

LED Grow Lights:

  • If you have a small collection of violets, then these types of LED grow lights may work well for your use.
  • I personally do not have experience using these, though have read and heard of many African violet growers using these with success.
  • The advantage of these bulbs is that they combine both warm and cool LED diodes into single bulbs, this allows for balanced light emission.
  • These bulbs are different from regular indoor LED bulbs; they are specifically designed for growing plants.
  • These grow lights have long arms with LED diodes underneath the arms.
  • These bulbs are available in different ranges of watts (wt), from 30W-60W. Watt is a measurement of energy consumption. Watt also correlates with lumens. If the wt of the bulb is low, the lumen is low. If the wt of the bulb is high, the lumen is high.
  • Few things you have to be careful with these LED bulbs are too much light.
  • You may have to adjust the timing the lights are on and the distance of the bulbs from the plant.
  • The good thing about this set up is that each individual arm is adjustable and each arm has its own adjustable timer.
  • You will have to find your own setting of timing and height which works for you in your own plant area.

LED Light Strips:

  • Another option for LED lighting are the LED light strips. These strips are available in different ranges of watts (wt), from 30W-90W.
  • They can be attached directly to the stand shelves using the adhesive tape on the back of the lights. Some of these lights come with magnets, so they can stay in place on the stands.
  • I have not personally tried these lights, but maybe down the road will try on one shelf.
  • If you do not want to buy LED tube light fixtures or do not want to reuse your fluorescent fixtures, these may be a nice option.
  • I would recommend starting slow with these, maybe trying them on one shelf or just a few plants first, to see how they do.
  • Some of the better quality LED light strips come with dimmers, so you can control the brightness, which is a nice feature to have, as you cannot adjust the height of your strips as you can with fixtures. Unless you change the height of your overall shelf, the LED light strips, pretty much stay in place. Though, these dimmers may need to be purchased separately.
  • Another feature of these LED light strips is that they can be cut to any desired length. This is a good feature, as you can increase the number of strips you can add.
  • There are also LED strips which do not required to be cut, they come as individual strips and are already connected to each other.
  • When purchasing these lights, make sure they come with a power adapter or transformer, sometimes these lights maybe cheap, but those come without a power adapter or transformer.
  • When deciding what kind of LED light strips to buy for your African Violets, its best to stick with daylight or white daylight. They will provide an even balance of light.
  • The daylight or white daylight LED light strips are not designed for growing plants; they are for household use, so you may have to play around with the hours the lights are on and the number of strips you attach to the stand.
  • Recently there have been LED light strips for plants which are reasonably priced and with lots of options. They are dimmable, so you can adjust the brightness ranging from 25%, 50%, 75% and 100%. They have a timer, adjustable for 3, 6, 9 or 12 hours a day.
  • These lights are available in different wavelengths, red, blue, green and/or yellow. The red wavelengths range from 640nm – 660nm, it promotes flowering and seed germination. The blue wavelengths range from 440nm – 470nm, it promotes chlorophyll absorption, root and green leafy growth. The green wavelengths are 495nm-570nmThe yellow wavelengths are 570nm-590nm
  • A mixture of red/blue wavelengths are also available, these can work well for African Violet plants as it promotes strong healthy stems/leaves and flowering.
  • Using only red or blue wavelengths long term will not work for African Violet plants as it emits only a narrow band of lights which can lead to stunted growth.
  • A full spectrum LED light strip can also work for African Violet plants, especially those with a higher ratio of red/blue wavelengths mixed in with green and yellow wavelengths. These strips can provide a balanced mixture of lights.
  • There are also expensive LED light strips for plants, but they are high intensity lights. They are meant for growing indoor seedlings or vegetable plants and may not be suitable for violets.

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